1. Field of the Invention
The present invention relates generally to the manufacture and use of novel honeycomb articles.
2. Technical Background
The desire for faster, more powerful integrated circuits has led to rapid development of advanced ultraviolet photolithographic methods. The performance of an integrated circuit increases as the feature size decreases; hence, a decrease in feature size allows more circuitry to be put on a chip of a given size, and reduces the power needed for operation. The feature sizes obtainable in a photolithographic process depend on the wavelength of radiation used in the exposure step; shorter wavelengths enable smaller feature sizes. As such, there has been a trend toward shorter wavelengths in photolithographic processes. Currently, photolithography systems based on wavelengths as low as 193 nm and 157 nm are being developed for commercial use.
In order to further decrease the minimum feature size obtainable in photolithographic processes, it has been suggested to use extreme ultraviolet (EUV) radiation, for example, having a wavelength of about 13 nm. The use of EW radiation in photolithography, while greatly reducing feature size, forces a radical departure in design from currently used photolithographic apparati. First, no practical materials are sufficiently transparent to EUV radiation to be used as windows, lenses or photomasks. As such, any manipulation of the radiation must be performed using reflection. Mirrors constructed from alternating layers of molybdenum and silicon have been used as reflecting focusing mirrors, collimators, and photomasks in EUV apparati.
Further, EUV sources tend to be rather dirty. In one conventional EUV source, a high energy laser is used to heat an object, which functions as a source of secondary emission of mainly shortwave radiation. This process releases undesirable particles and atoms, forming debris in the apparatus. The debris, known generally herein as “soot,” can deposit on the mirrors and on the photomask, wreaking havoc with the necessarily precise optical system of the EUV apparatus. Since there currently exists no suitable window material for EUV radiation, the design of a device to catch the particulate matter while transmitting the EUV radiation is not trivial. One suggestion for an EUV soot filter is described in international patent application publication WO 99/42904, which is incorporated herein by reference. The apparatus described therein is placed between the EUV source and optical system, and has a plurality of foils or plates arranged in a direction radial from the EUV source. The position of the plates allows any EUV radiation propagating directionally from the EUV source to the optical system to be transmitted, but will catch the randomly diffusing soot. The filter is assembled from a plurality of copper plates; such a filter would be difficult to assemble, especially as the desired size of the filter increases. It would be desirable to have an EUV soot filter that is simple to fabricate and easily adaptable to a number of EUV source geometries.